By USC Health Sciences Public Relations and Marketing

A new study from the USC Norris Comprehensive Cancer Center shows targeting both hormone receptors (HRs) and human epidermal growth factor receptor 2 (HER2) in first-line treatment of metastatic breast cancer (MBC) patients significantly increased overall survival times.

A team of researchers led by Debu Tripathy, professor of medicine at the Keck School of Medicine of USC, looked at data provided by RegistHER, a prospective, observational study of 1,023 newly diagnosed HER2-positive metastatic breast cancer patients. They found that hormonal therapy given with the anti-HER2 antibody trastuzumab (Herceptin) and chemotherapy is associated with improved survival and progression-free survival outcomes, compared to no hormonal therapy.

The study, titled “First-Line Treatment Patterns and Clinical Outcomes in Patients with HER2-Positive and Hormone Receptor-Positive Metastatic Breast Cancer from RegistHER,” appears in The Oncologist, the peer-reviewed journal of the Society for Translational Oncology.

“This study can aid in significantly improving treatment planning and shared decision-making with patients,” Tripathy said. “It provides a platform for considering hormonal therapy as a standard component of treatment regimens for patients with HER2-positive and hormone receptor-positive metastatic breast cancer.”

Using data from RegistHER, a multicenter, prospective cohort registry study, the research team determined that the targeting of both hormone and HER2 receptors is associated with better outcomes compared to HER2-based therapy alone. HER2-positive breast cancer, which accounts for about 25 percent of breast cancers diagnosed, tends to be more aggressive than other types of breast cancer because it promotes the growth of cancer cells.

About half of HER2-positive breast cancer cases are also estrogen receptor-positive. Trastuzumab specifically targets HER2 cells and is the standard of care for patients with HER2-positive breast cancer, while HR-positive breast cancer is treated with hormonal therapy designed to interfere with HR signaling.

A lack of uniformity in how hormone therapy is used in treating HER2-positive breast cancer complicates the registry study analysis, but adjustments showed consistent improved progression-free survival times and even overall survival rates, with the addition of hormone therapy to either trastuzumab alone or with chemotherapy.